On Monday, we took a fresh look at the Senate landscape on the heels of Scott Brown's announcement that he will run in New Hampshire. The conclusion? Republicans have more reasons than perhaps at any previous point this election cycle to be bullish about winning back the majority.

(Andrew Harrer/Bloomberg

Today comes more evidence the tide is shifting in Republicans' favor. The nonpartisan Cook Political Report --a widely respected independent political handicapper -- moved a trio of Democratic-held seats from "Lean Democratic" to "Toss-up." In addition, Brown's entrance moved New Hampshire from "Likely Democratic" to "Lean Democratic," meaning it looks more likely to fall into Republican hands than before.

Here's Cook Report's Jennifer Duffy:

Sens. Mark Begich in Alaska, Mary Landrieu in Louisiana, and Kay Hagan in North Carolina are moving to the Toss Up column. In each of these races, polls show the races generally within the margin of error tied. Democratic Sen. Mark Pryor in Arkansas, who has been in the Toss Up column for months, has comparable numbers to these incumbents. Democrats say that Pryor has not been so much as a single point behind in any of their polls in months, suggesting that rumors of his demise might be premature. At this point it has become something of a D.C. parlor game to guess which of the four – Begich, Landrieu, Hagan or Pryor – is in the most trouble. At this point, it is pretty much splitting hairs. All four are locked into very close races, but none is dead.

When GOP Rep. Cory Gardner announced his bid against Democratic Sen. Mark Udall in Colorado three weeks ago, we moved that race to Lean Democratic. With former U.S. Sen. Scott Brown’s announcement that he would challenge Democratic Sen. Jeanne Shaheen, New Hampshire also goes into the Lean Democratic column.

There is some good news for Democrats in Cook's new ratings. Georgia moved from "Lean Republican" to "Toss-up." It's one of Democrats' only two realistic pickup opportunities this cycle, along with Kentucky. Mississippi moved from "Solid Republican" to "Likely Republican." The state is still a very good bet to stay in GOP hands, but if nominated, Sen. Thad Cochran's GOP primary challenger Chris McDaniel might pose problems for his party in the general election against former congressman Travis Childers (D). Finally, Senate seats in Hawaii and Massachusetts look safer for Democrats.

With the new moves, eight Democratic seats now fall into Cook Report's "Toss-up," "Lean Republican" or "Likely Republican" categories: Alaska, Arkansas, Louisiana, Michigan, North Carolina, Montana, West Virginia and South Dakota. Just two GOP seats fall into the corresponding Democratic categories: Georgia and Kentucky.

Republicans need to net six seats for the majority. In addition to the eight ripest opportunities above, they also stand chances of picking up Colorado and New Hampshire -- chances that did not exit before Gardner and Brown entered the mix. There's also Iowa, a Democratic seat worth watching, even as the Republican field has struggled and Democratic Rep. Bruce Braley (D) has done well so far.

The overarching reason Republicans should be optimistic is that they have more paths to the majority than at any point this cycle so far.

So are Republicans now in the driver's seat for the majority? No, says Duffy, who says it's still a toss-up, or a "jump ball." Democrats have put themselves in a position to go on offense in two states and are still confident their most vulnerable incumbents can run hyper-local campaigns capable of defying an unfavorable national climate. They have done this before. Just ask Sens. Heidi Heitkamp (D-N.D.) and Jon Tester (D-Mont.).

But if you would have asked Republicans a year ago whether they'd take a "jump ball" at this point in 2014 on the heels of more and more races trending in their favor as outside GOP money continues to flood in on their behalf, we bet they'd have taken it.